Electronic camera

ABSTRACT

The present invention relates to an electronic camera which images an object image and records image data. Particularly, the present invention relates to technology to record image data in a good shooting state, such as with little blurring due to hand shaking. The invention has an image pick-up means which continuously images an object, a temporary memory means which temporarily stores a plurality of frames of image data which are continuously imaged by the image pick-up means, a shooting evaluation means which evaluates a good or bad shooting state of the image data imaged by the image pick-up means, a still image selection means which selects the image data with the highest evaluation of the shooting evaluation means among the image data which are stored in the temporary memory means, and an image saving means which saves the image data which is selected by the still image selection means.

This is a Continuation of U.S. patent application Ser. No. 12/839,763filed Jul. 20, 2010, which in turn is a Continuation of U.S. patentapplication Ser. No. 11/349,975 filed Feb. 9, 2006, which in turn is aDivision of U.S. patent application Ser. No. 09/149,001 filed Sep. 8,1998, which claims priority to Japanese Patent Application No. 10-236102filed Aug. 21, 1998. The disclosure of the prior applications are herebyincorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electronic camera which photographsan object and records image data. In particular, the present inventionrelates to a technology for recording image data in a good shootingcondition without hand shaking or the like.

2. Description of the Related Art

Generally, when performing hand-held camera shooting, hand shaking oftenoccurs. When this kind of hand shaking occurs, since an object field isexposed in a blurry condition, an entirely blurry image is shot.

In a blurry image like this, the details of the entire image and theedge portions, which should be shot clearly, are lost. Therefore, theimage does not give a good impression.

A conventional camera with a hand shaking correction mechanism forsolving these disadvantages due to hand shaking is well known.

FIG. 13 shows a camera with this kind of hand shaking correctionmechanism.

In FIG. 13, a shooting lens 92 is disposed on the front face of thecamera 91. A blur correction optical system 93 is rotatably arranged inthe lens barrel of the shooting lens 92.

The rotation of two-axis coreless motors 94 and 95 is transmitted tothis blur correction optical system 93, causing it to vibrate verticallyand horizontally.

Meanwhile, a blur amount detecting sensor 96 which detects the bluramount in the horizontal direction and a blur amount detecting sensor 97which detects the blur amount in the vertical direction are arranged inthe camera 91.

In the camera 91 which has this kind of structure, vibration of thecamera body is detected by using the blur amount detecting sensors 96and 97. The camera 91 drives the coreless motors 94 and 95 in thereverse direction of the detected vibration, and vibrates the opticalaxis of the blur correction optical system 93. As a result, thevibration of the shooting optical axis is diminished, and a goodphotograph in which the hand shaking is corrected can be shot.

However, in this kind of conventional example, the blur correctionoptical system 93 is disposed in the shooting lens 92. Therefore, thereis a problem in that the shooting lens 92 becomes large and heavy.

Moreover, the space to arrange the blur correction optical system 93 hasto be kept in the shooting lens 92, and there is a problem in that theflexibility of design of the shooting lens 92 decreases.

Furthermore, the inner reflection in the shooting lens 92 increases forthe portion where the blur correction optical system 93 is provided.Therefore, flaring easily occurs when performing back-lit shooting orthe like.

Moreover, since electric power is consumed when driving the blurcorrection optical system 93, there is a problem in that the batterylife becomes shorter.

Furthermore, there is a problem in that a small amount of noise occurswhen driving the blur correction optical system 93.

On the other hand, a blurred image can occur due not only to theaforementioned hand shaking, but also due to object shifting andmisfocusing. However, since the conventional hand shaking correctionmechanism only diminishes the vibration of the camera, there is aproblem in that the mechanism cannot prevent object shifting andmisfocusing at all.

In particular, along with the trend toward higher resolution andminiaturization of imaging elements in recent years, the light receivingarea per one pixel is more and more reduced, and the effectivesensitivity of the imaging element has become low. Because of this,there is a tendency that the exposure time of the shooting elementgenerally increases, and the chances of occurrence of hand shaking andobject shifting become even higher. Because of this, especially in anelectronic camera, immediate countermeasures are desired with respect tohand shaking and object shifting.

Moreover, it was very difficult to accurately prevent misfocusaccurately with conventional AF (automatic focus) shooting for an objectwhich shows unpredictable movements, such as a flower which is swayingin the wind. Because of this, an electronic camera which can accuratelyresolve the misfocus accurately under this adverse conditions isstrongly desired.

SUMMARY OF THE INVENTION

The present invention, in order to solve the aforementioned problems,has a purpose of providing an electronic camera which can reliablyobtain image data in a good shooting condition, an electronic camerawhich can achieve minimum electric power consumption, an electroniccamera which can decrease the worst value of release time lag byapproximately one half, an electronic camera with a simplifiedstructure, and an electronic camera which can decrease the memorycapacity of the temporary storing means (later mentioned) or canincrease the number of the samplings of image data.

Moreover, another purpose of the invention is to provide an electroniccamera which can omit the temporary storing means (later mentioned), anelectronic camera which can obtain good image data with little handshaking, an electronic camera which can obtain good image data which haslittle object shifting or misfocus, an electronic camera which caneffectively perform analysis of a spatial frequency component, and anelectronic camera which can obtain good image data with little releasetime lag.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a principal block diagram which explains the invention.

FIG. 2 is a principal block diagram which explains another aspect of theinvention.

FIG. 3 is a block diagram which shows the first embodiment.

FIG. 4 is a flowchart which explains the operation of the firstembodiment.

FIG. 5 is a figure which shows the time change of the blur amount.

FIG. 6 is a block diagram which shows the second embodiment.

FIG. 7 is a flowchart which explains the operation of the secondembodiment.

FIG. 8 is a block diagram which shows the third embodiment.

FIG. 9 is a flowchart which explains operation of the third embodiment.

FIG. 10 is a block diagram which shows the fourth embodiment.

FIG. 11 is a flowchart which explains the operation of the fourthembodiment.

FIG. 12 is a flowchart which explains the operation of the fifthembodiment.

FIG. 13 is a diagram which shows a conventional example of a camera witha hand shaking correction mechanism.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a schematic block diagram that explains the invention.

The invention comprises an image pick-up means 1 which continuouslyimages an object, a temporary memory means 2 which temporarily stores aplurality of image data that are continuously imaged by the imagepick-up means 1, a shooting evaluation means 3 which evaluates whetherthe shooting condition of the image data which is imaged by the imagepick-up means 1 is good or bad, a still image selection means 4 whichselects image data with the highest evaluation by the shootingevaluation means 3, and an image saving means 5 which saves the imagedata which is selected by the still image selection means 4.

In the electronic camera, the temporarily memory means 2 starts thetemporary storing of the image data after the release operation of theelectronic camera is performed.

Moreover, while waiting for the release operation, the temporary memorymeans 2 successively takes in new image data from the image pick-upmeans 1 and successively updates the image data that is beingtemporarily stored, and after the release operation of the electroniccamera, suspends the data updating when the image data spanning frombefore to after the release operation has been temporarily stored.

The temporary memory means 2 and the image saving means 5 share the samememory mechanism.

The temporary memory means 2 performs differential compression andstores a plurality of image data that is continuously imaged by theimage pick-up means 1.

FIG. 2 is a schematic block diagram to explain another aspect of theinvention.

Another aspect of the invention comprises the image pick-up means, thatcontinuously images an object, a memory medium 10 which can store theimage data, a shooting evaluation means 3 that evaluates whether theshooting condition of the individual image data imaged by the imagepick-up means 1 is good or bad, a comparison means 11 which compares theevaluation of the shooting evaluation means 3 concerning the image datain the memory medium 10 and the evaluation of the shooting evaluationmeans 3 concerning new image data from the image pick-up means 1, and animage overwriting means 12 which overwrites and records the new imagedata to the memory medium 10 when the evaluation of the new image databy the comparison of the comparison means 11 is high.

This shooting evaluation means 3 is a means for detecting the bluramount of the image pick-up means 1 as at least one of a good shootingcondition or a bad shooting condition.

In particular, the shooting evaluation means 3 evaluates the spatialfrequency component of the image data as at least one of a good shootingcondition and a bad shooting condition.

Furthermore, the shooting evaluation means 3 evaluates the high areacomponent amount of the spatial frequency based on the compressionencoding amount of the image data.

The shooting evaluation means 3 evaluates the release time lag which isthe time shift between the release operation of the electronic cameraand the point of imaging the image data.

[Explanation of the Operation of FIG. 1]

In the electronic camera of FIG. 1, the image pick-up means 1continuously images an object. A plurality of image data that are shotin the same manner are temporarily stored in the temporary memory means2.

Meanwhile, the shooting evaluation means 3 evaluates whether theshooting condition of the individual image data is good or bad. Thestill image selection means 4 selects the image data which is imagedduring the period when the evaluation of the shooting condition ishighest among the image data that are stored in the temporary memorymeans 2. The image saving means 5 saves the selected image data.

According to the aforementioned operation, the electronic camera canselectively obtain image data of a good shooting condition.

Moreover, in particular, in this electronic camera, the temporary memorymeans 2 temporarily stores the image data during the shooting period.Accordingly, since it is sufficient to perform the selecting processingof the image data after the shooting is completed, the processingoperation during the shooting period can be decreased without anytrouble.

In the electronic camera, the temporary memory means 2 starts thetemporary storing of the image data after the release operation of theelectronic camera.

Accordingly, image data of a good shooting condition can be selectedfrom among the image data that is imaged after the release operation.

With this kind of operation, the operation may start after the releaseoperation, and it is not necessary to always perform the imagingoperation. Accordingly, it is possible to minimize electric powerconsumption of the electronic camera.

In the electronic camera, the temporary memory means 2 takes the newimage data from the image pick-up means 1 successively while waiting forthe release operation.

The temporary memory means 2 updates the image data by using this newimage data, and maintains a plurality of image data that are temporarilystored in the nearest condition.

When the electronic camera is release-operated in this condition, thetemporary memory means 2 suspends the data updating when the image dataspanning from before to after the release operation has been temporarilystored.

Through this operation, the sampling zone (interval) of the image datawhich remains in the temporary memory means 2 is the zone which spansfrom before to after the release operation.

In particular, hand shaking that accompanies the release operationhardly ever occurs right before the release operation. Because of this,the possibility of selecting image data which has fewer hand shakingsbecomes very high by adding the period of right before the releaseoperation to the sample zone.

In addition, since the sample zone of the image data spans from beforeto after the release operation, the worst value of the release time lag(corresponding to the time interval between the edge point of the samplezone and the release operation point) decreases by approximately halfcompared to when a sample zone of the same time length is arranged onlyafter the release operation.

In the electronic camera, the temporary memory means 2 and the imagesaving means 5 share the same memory mechanism. Accordingly, thestructure of the electronic camera is simplified.

In the electronic camera, the temporary memory means 2 performsdifferential compression to the image data which is continuously imagedby the image pick-up means 1 and stores the image data. The differentialcompression is compression by obtaining differential data between imagesand, for example, includes the techniques of simple differentialcompression between frames, movement guarantee prediction or the like.Normally, image data which is continuously imaged by the image pick-upmeans 1 has a very high correlation, even though it is not as high asthe frame correlation of an animated image. Accordingly, it is possibleto make the encoding amount of the image data smaller by performing theabove mentioned differential compression.

Accordingly, it is possible to increase the sample number of the imagedata which can be stored in the temporary memory means 2. Thepossibility of selecting image data which has a better shootingcondition becomes high by thus increasing the sample number of the imagedata.

Moreover, if the sample number of image data is not increased, it ispossible to decrease the memory capacity of the temporary memory means2.

[Explanation of the Operation of FIG. 2]

In the electronic camera of FIG. 2, the image pick-up means 1continuously images an object. At this time, the shooting evaluationmeans 3 evaluates whether the shooting condition is good or bad. Thecomparing means 11 compares the evaluation concerning image data in thememory medium 10 and the new evaluation concerning new image data fromthe image pick-up means 1.

Here, when the new evaluation is higher, the image overwriting means 12overwrites and records the new image data to the memory medium 10. As aresult, the image data of the better shooting condition remains in thememory medium 10.

In particular, in this electronic camera, it is not necessary totemporarily store the entire series of image data, and a large capacityof temporary memory means becomes unnecessary.

The electronic camera detects the blur amount (vibration amount orangular speed) of the image pick-up means 1 for the good or badevaluation of the shooting condition. It can be evaluated that the handshaking is small and the shooting condition is good when the blur amountof the image pick-up means 1 is small.

Accordingly, it is possible to image the image data with less handshaking by performing the good or bad evaluation of the shootingcondition by using the blur amount of the image pick-up means 1 as themeasurement.

The electronic camera uses the spatial frequency component of the imagedata as the measurement of the good or bad evaluation of the shootingcondition. Normally, for image data that are continuously imaged theimage itself does not change much and it is assumed that thedistribution of the spatial frequency has virtually no change. However,when hand shaking, object shifting or misfocus occurs to these imagedata, the image data is flattened and spatial frequency components ofthe high area is lost.

Accordingly, it can be evaluated that image data which has many spatialfrequency components of high area among these image data has less handshaking, object shifting or misfocus as a whole, and that the shootingcondition is better.

Accordingly, it is possible to accurately select the image data whichhas small hand shaking, object shifting and misfocus as a whole byperforming the good or bad evaluation of the shooting condition by usingthe spatial frequency component of the image data as the measurement.

The electronic camera evaluates the spatial frequency component of theimage data from the compressed encoding amount. Normally, it can beevaluated that when the compressed encoding amount is larger, thespatial frequency component of the high area is larger. Accordingly,image data among the image data that are continuously imaged which has alarge compressed encoding amount has less hand shaking, object shifting,and misfocus as a whole, and it can be evaluated that the shootingcondition is better. Moreover, the value of this kind of compressedencoding amount can be obtained from the result of prior imagecompression processing, and it is not necessary to add specialprocessing.

The electronic camera detects the release time lag as at least one of agood evaluation and a bad evaluation of the shooting condition. Whenthis release time lag is smaller, it is closer to the shutter timingwhich the user desires, and it can be evaluated that the shootingcondition is better. Accordingly, it is possible to select image datawhich has a smaller release time lag by making the release time lag asone item of the good or bad evaluation.

Moreover, in particular, the case is explained in which image data whichhas smaller release time lag is selected in a condition of performingthe temporary storing of the imaged image from before the releaseoperation. In this case, it is possible that the camera is in the middleof an exposure operation at the moment of the release operation.Accordingly, it is possible to obtain an image which has completely zerorelease time lag, which could not be obtained with conventional singleshooting of an electronic camera, by automatic image selection.

Moreover, in the above description, the good or bad evaluation isperformed by only one evaluation item for convenience. However, thepresent invention is not limited to this.

The good or bad evaluation can be performed by providing a priorityorder in the plurality of evaluation items, or by performing a totalevaluation by weighting the evaluation items. At this time, needless tosay, it is acceptable when evaluation items other than those in claims7-10 are included.

Moreover, the electronic camera of the above-mentioned FIGS. 1 and 2 isnot narrowly limited to a single structure electronic camera. There is atrend in recent electronic cameras to structure them as a plurality ofmechanical systems, such as by having separate structures for theshooting unit and the information mechanism. (Computer, electronicnotebook or the like). In this kind of system structure, it is possibleto divide the operations of the present invention appropriately betweena plurality of machines.

For example, it is possible to divide the operations, such as (1) in theimaging unit side, the continuously shot image data is temporarilystored and (2) in the information mechanism side, the images areselected and saved from among the series of image data according to thegood or bad evaluation of the shooting condition.

Moreover, the operation of the information mechanism in this case can berealized by using a program (recorded on a machine readable recordingmedium) which makes the information mechanism execute “a step ofobtaining a result of a good or bad evaluation from the image pick-upunit or performing a good or bad evaluation of the shooting conditionfrom the spatial frequency component of the image data or the like” and“a step of selecting and saving image data according to the result ofthe good or bad evaluation”.

Embodiments

Hereafter, the embodiments of the present invention are explained basedon the drawings.

First Embodiment

FIG. 3 is a block diagram which shows the first embodiment. Moreover,the first embodiment corresponds to the invention of claims 1, 2, 4, 5and 7.

In FIG. 3, a shooting lens 22 is provided at the front face of theelectronic camera 21. The light receiving face of an image pick-upelement 23 is arranged on the image space side of the shooting lens 22.

The image output of this image pick-up element 23 is directly stored inthe image memory 25 via an image processor 24 which performs colorsignal processing, A/D conversion, γ correction, image compression andthe like. Other than this, in the image memory 25, reading and writingof the data are performed via the data bus of the microprocessor 26.

Moreover, blur amount detecting sensors 29 a and 29 b that are made ofan angular speed sensor such as a piezoelectric gyro are arranged withinthe case of the electronic camera 21. The blur amount detecting sensor29 a detects the blur amount in the vertical direction (pitching). Theother blur amount detecting sensor 29 b detects the blur amount in thehorizontal direction (yawing). Output terminals of these blur amountdetecting sensors 29 a and 29 b are respectively connected to the A/Dinput terminal of the microprocessor 26.

Moreover, on the top face of the case of the electronic camera 21, arelease button 30 is arranged. The switch output of the release button30 is connected to the microprocessor 26.

Moreover, an electronic shutter control signal from the microprocessor26 is given to the CCD driving circuit 31. The CCD driving circuit 31forms a driving pulse corresponding to this control signal, and gives itto the image pick-up element 23. In addition, a timer 32 and an infraredray transmission interface 33 are connected to the microprocessor 26.

Moreover, the corresponding relationships of the present invention andthe first embodiment are as follows. Image pick-up means 1 correspondsto the image pick-up element 23 and the CCD driving circuit 31. Thetemporary memory means 2 corresponds to the image memory 25 and “afunction which differentially compresses and temporarily stores imagedata” of the image processor 24. The shooting evaluation means 3corresponds to the blur amount detecting sensors 29 a and 29 b. Thestill image selection means 4 corresponds to “a function which selectsimage data based on the blur amount” of the microprocessor 26. The imagesaving means 5 corresponds to the image memory 25 and “a function whichsaves the selected image data” of the microprocessor 26.

Next, the operation of the first embodiment is explained.

FIG. 4 is a flowchart to explain the operation of the first embodiment.

First of all, when the main power of the electronic camera 21 is turnedon, the microprocessor 26 waits until the release button 30 is pressed(NO side of S1 of FIG. 4).

Here, when the release button 30 is pressed (YES side of S1 of FIG. 4),the microprocessor 26 activates the CCD driving circuit 31, andtemporarily discharges the unnecessary charge on the image pick-upelement 23. After discharging the unnecessary charge, a signal charge isnewly accumulated on the image pick-up element 23 corresponding to thebrightness of an object which is projected to the light receiving face(S2 of FIG. 4).

During the accumulating period of this kind of signal charge, themicroprocessor 26 takes in a blur amount W1 in the vertical directionfrom the blur amount detecting sensor 29 a. A blur amount W2 in thehorizontal direction is obtained from the other blur amount detectingsensor 29 b. The microprocessor 26 calculates the sum of the squares orthe sum of the absolute values of the blur amounts W1 and W2, and takesthis value as the blur amount W of the entire electronic camera 21 (S3of FIG. 4). When a predetermined accumulation time passes, themicroprocessor 26 reads out the image data from the image pick-upelement 23 via the CCD driving circuit 31 (S4 of FIG. 4).

The image processor 24 records this image data in a temporary memoryarea of the image memory 25 after performing A/D conversion, γcorrection, image compression and the like. Moreover, for the imagecompression here, differential compression is adopted which is the sameas in MPEG or the like. Moreover, at this time, the microprocessor 26records the blur amount W relating to the image data (S5 of FIG. 4).

The above mentioned series of operations S2-S5 are repeatedly executeduntil a limited time of 0.3 seconds elapses from the release operation(YES side of S6 of FIG. 4).

Through the operation until this point, image data of a plurality framesthat are imaged during the 0.3 seconds from the release operation arerecorded in the image memory 25 along with the blur amount W during theshooting period.

The microprocessor 26 searches for the smallest value among the bluramounts W, and finds image data A which was imaged during the period forwhich the smallest blur amount W is detected (S7 of FIG. 4).

FIG. 5 is a diagram which shows the condition of the time change andoverall blur amount W. According to FIG. 5, it can be expected that theblur amount W becomes smallest approximately once for every 0.3 seconds.Accordingly, the image data A which is selected as described above hassufficiently small hand shaking and it is predicted that it is goodimage data.

The microprocessor 26 records this image data A in the saving area ofthe image memory 25 (S8 of FIG. 4). Moreover, it is acceptable to finishthe processing of the image data A by performing a change of themanagement area, the image memory 25 and the file attributes withoutactually shifting the image data A in the image memory 25. Moreover,when the image data A is differentially compressed, it may be newly JPEGcompressed after being image decompressed.

By the operation explained above, in the first embodiment, the imagedata which has the smallest blur amount W among the image data that arecontinuously imaged is selected. Accordingly, it is possible to obtainimage data which has small hand shaking without using a conventionalhand shaking correction mechanism at all.

Moreover, since it is not necessary to arrange an optical system for thehand shaking correction in the shooting lens 22, a compact lightweightshooting lens 22 can be easily obtained.

In addition, because there is no need to maintain space in order toarrange the optical system for hand shaking correction in the shootinglens 22, the degree of design freedom of the shooting lens 22 becomeshigher. Because of this, it has become possible to improve theoperationability of the shooting lens 22 without having any problems.

Moreover, since the inner reflection by the optical system for the handshaking correction is resolved, flaring at the time of performingbacklight shooting is decreased.

In addition, since there is no need to have a driving mechanism for thehand shaking correction, it is possible to extend the battery life toconserve the electric power consumption. Moreover, the disadvantages ofoccurrence of noise or vibration from the driving mechanism for the handshaking correction are resolved.

Moreover, since the image memory 25 is jointly used for both thetemporary storing and saving of the image data, there is no need toprovide the image memory separately, and the structure of the electroniccamera 21 can be simplified.

Moreover, in the above mentioned embodiment, the memory area of theimage memory 25 is fixedly divided into the temporary memory area andthe saving area, but the present invention is not limited to this. Forexample, it is acceptable to movably divide the temporary memory area ofthe image memory 25. With this kind of structure, it becomes possible tosave the image data by using the entire memory area of the image memory25 by dividing the temporary memory area into the saving area gradually.

Next, another embodiment is explained.

Second Embodiment

FIG. 6 is a block diagram which shows the second embodiment. Moreover,the second embodiment corresponds to the invention that is described inclaims 1, 3, 7 and 10.

In FIG. 6, a shooting lens 42 is provided on a front face of theelectronic camera 41. The light receiving face of an image pick-upelement 43 is arranged on the image space side of the shooting lens 42.

The image output from the image pick-up element 43 is connected to thedata input of the image memory 45 via the image processor 44 whichperforms color signal processing, A/D conversion, γ correction and thelike. Meanwhile, the data output of the image memory 45 is connected tothe data input of the microprocessor 46.

A memory card 48 is detachably connected to the data output terminal ofthe microprocessor 46 via the image recording part 47.

Meanwhile, blur amount detecting sensors 49 a and 49 b that are composedof an angular speed sensor such as a piezoelectric gyro are arrangedwithin the case of the electronic camera 41. The outputs of these bluramount detecting sensors 49 a and 49 b are respectively connected to A/Dinput terminals of the microprocessor 46.

Furthermore, a release button 50 is arranged on the top face of the caseof the electronic camera 41, and the switch output of the release button50 is connected to the microprocessor 46.

An electronic shutter control signal from the microprocessor 46 is givento the CCD driving circuit 51. The CCD driving circuit 51 generates adriving pulse in response to this control signal, and forwards it to theimage pick-up element 43. Other than this, a timer 52 is connected tothe microprocessor 46.

The corresponding relationships of the present invention and secondembodiment are as follows. The imaging means 1 corresponds to the imagepick-up element 43 and the CCD driving circuit 51, the temporary memorymeans 2 corresponds to the image memory 45 and “a function thattemporarily stores the image data spanning from before to after therelease operation” of the image processor 44, the shooting evaluationmeans 3 corresponds to the blur amount detecting sensors 49 a and 49 band “a function which measures the release time lag” of the timer 52 andthe microprocessor 46, the still image selection means 4 corresponds to“a function which selects the image data based on an evaluation value”of the microprocessor 46, and the image saving means 5 corresponds tothe image recording part 47 and the memory card 48.

Next, the operation of the second embodiment is explained.

FIG. 7 is a flowchart which explains the operation of the secondembodiment.

First of all, when the main power of the electronic camera 41 is turnedon, the microprocessor 46 discharges unnecessary charges in the imagepick-up element 43 via the CCD driving circuit 51. After thusdischarging unnecessary charges, signal charges are accumulated in theimage pick-up element 43 according to the brightness of the object whichis projected on the light receiving face (S11 of FIG. 7).

During the accumulation period of the signal charge, the microprocessor46 obtains the blur amount W1 in the vertical direction from the bluramount detecting sensor 49 a. The blur amount W2 in the horizontaldirection is obtained from the other blur amount detecting sensor 49 b.The microprocessor 46 calculates the sum of the square values, the sumof the absolute values or the like for these blur amounts W1 and W2, andtakes this as the overall blur amount of the electronic camera 41 (S12of FIG. 7).

Next, the microprocessor 46 obtains the current time as the shootingtime Te from the timer 52 (S13 of FIG. 7).

In this condition, when a predetermined accumulation time has passed,the microprocessor 46 reads out the image data from the image pick-upelement 43 via the CCD driving circuit 51 (S14 of FIG. 7).

The image processor 44 temporarily stores this image data in the imagememory 45 after performing A/D conversion, γ correction, and the like(S15 of FIG. 7). At this time, the microprocessor 46 stores the bluramount W and the shooting time Te in correlation with the image data(S17 of FIG. 7).

When the image data and the image memory 45 have already reached up toseven frames (S16 of FIG. 7), the newest data is written and recorded inplace of the oldest data in the image memory 45 (S18 of FIG. 7).

Here, the microprocessor 46 evaluates whether the release button 50 ispressed (S19 of FIG. 7).

When the release button 50 is pressed (YES side of S19 of FIG. 7), themicroprocessor 46 obtains the current time from the timer 52, and storesit as the time Tr of the release operation (S20 of FIG. 7).

The above-mentioned operations S11-20 are repeatedly executed until fourframes of the image data after the release operation have been recorded(NO side of S21 of FIG. 7).

On the other hand, when four frames of the image data have been recordedafter the release operation (YES side of S21 of FIG. 7), themicroprocessor 46 executes the selection of the image data by thefollowing procedure after suspending the imaging operation.

First of all, the microprocessor 46 calculates the evaluation value E byusing the equation (1) for each image data in the image memory 45 (S22of FIG. 7).

Evaluation value E=α·|Te−Tr|+β·|W|  (1)

Here, the first item of the right side is an item relating to therelease time lag, and the second item is an item relating to the bluramount W. Additionally, the coefficients α and β are to perform theweighting of these two items (for example, they are set as α=1, β=1 orthe like).

The microprocessor 46 searches for the smallest value among individualevaluation values E, and finds the image data A which is related to thesmallest evaluation value E (S23 of FIG. 7).

The microprocessor 46 reads out this image data A from the image memory45 and image compresses the data. The microprocessor 46 saves theimage-compressed image data A onto the memory card 48 via the imagerecording part 47 (S24 of FIG. 7). For the processing of the imagecompression, it is acceptable to complete it at steps S17 and S18 inFIG. 7 instead of performing it at this point.

Next, the microprocessor 46 returns the operation to step S11 afterinitializing the image memory 45 and the control data (S25 of FIG. 7).

According to the series of operations that are explained above, in thesecond embodiment, the image data in which the evaluation value E is thesmallest is selected among the continuously imaged image data.Accordingly, it is possible to obtain the image data in which the handshaking is smallest and in which the release time lag is smallest bytaking the evaluation value E as the standard.

Additionally, since the selection of the image data is performed fromamong image data spanning from before to after the release operation,more adequate image data can be selected without being limited to thedata obtained after performing the release operation.

In the above-mentioned second embodiment, the temporary storing of theimage data is started by turning on the main power, but the presentinvention is not limited to this. For example, it is acceptable for themicroprocessor 46 to detect the half-pressed state of the release button50 and to start the temporary storing of the image data from thehalf-pressed point. In this kind of structure, because it is notnecessary to always perform the temporary storing of the image data, itis possible to conserve electric power of the electric camera.

Next, another embodiment is explained.

The Third Embodiment

FIG. 8 is a block diagram showing the third embodiment.

In FIG. 8, a shooting lens 62 is fixed at a front surface of theelectronic camera 61. The light-receiving face of an image pick-upelement 63 is disposed on the image space side of the shooting lens 62.

The image output of the image pick-up element 63 is given to amicroprocessor 65 through an image processor 64, which performs colorsignal processing, A/D conversion, γ correction, and the like.Furthermore, an image memory 66 is connected to the data bus of themicroprocessor 65.

Additionally, a memory card 68 is detachably connected to the dataoutput terminal of the microprocessor 65 through an image recorder 67.

Furthermore, the blur amount detection sensors 69 a and 69 b comprisingan angular speed sensor such as a piezoelectric gyro are disposed insideof the case of the electronic camera 61. The outputs of the blur amountdetection sensors 69 a and 69 b are respectively connected to A/D inputterminals of the microprocessor 65.

In addition, a release button 70 is disposed on the top of the case ofthe electronic camera 61, and the switch output of the release button 70is connected to the microprocessor 65.

Additionally, an electronic shutter control signal from themicroprocessor 65 is given to a CCD driving circuit 71. The CCD drivingcircuit 71 forms a driving pulse in response to the control signal andgives it to the image pick-up element 63.

Furthermore, with respect to the corresponding relationships between theinvention as set forth in claims 6 and 7 and the third embodiment, theimage pick-up means 1 corresponds to the image pick-up element 63 andthe CCD driving circuit 71, the shooting evaluation means 3 correspondsto the blur amount detection sensors 69 a and 69 b, the recording medium10 corresponds to the image memory 66, the comparison means 11corresponds to a “function to perform comparison between old and newblur amount” of the microprocessor 65, and the image overwriting means12 corresponds to a “function to overwrite the image data to the imagememory 66” of the microprocessor 65.

The following explains the operation of the third embodiment.

FIG. 9 is a flow chart explaining the operation of the third embodiment.

First, when the main power is turned on to the electronic camera 61, themicroprocessor 65 determines the maximum allowable value of the bluramount, based upon the current shutter speed and focal distance (FIG. 9S31).

Next, the microprocessor 65 initially sets the maximum allowable valuewhich was thus determined at the minimum blur amount W_(min) (FIG. 9S32).

The microprocessor 65 returns to step S31 until the release button 70 ispressed, and the above operation is regularly repeated (NO side of FIG.9 S33).

Meanwhile, when the release button 70 is pressed (YES side of FIG. 9S33), the microprocessor 65 repeatedly performs steps S35-40 as followsfrom the time of the release operation until 0.5 second has elapsed(FIG. 9 S34).

First, the microprocessor 65 temporarily discharges unnecessary chargesfrom the image pick-up element 63 via the CCD driving circuit 71. Afterthus discharging unnecessary charges, the signal charge is accumulatedin response to the brightness of the object image which is projectedonto the light-receiving face in the image pick-up element 63 (FIG. 9S35).

During the accumulation period of the signal charge, the microprocessor65 obtains the blur amount W1 in the up-and-down direction from the bluramount detection sensor 69 a. The blur amount W2 in the right-and-leftdirection is obtained from the other blur amount detection sensor 69 b.The microprocessor 65 calculates the sum of the square values or the sumof the absolute values of the blur amounts W1 and W2, and this isdefined as the overall blur amount W of the electronic camera 61 (FIG. 9S36).

Here, the microprocessor 65 compares the size of the minimum blur amountW_(min) and the blur amount W.

As a result of this type of comparison, when the blur amount W is larger(NO side of FIG. 9 S37), the microprocessor 65 does not read the imagedata from the image pick-up element 63 and returns the operation to stepS34.

Furthermore, at the time of this determination, since the microprocessor65 discharges unnecessary charge from the image pick-up element 63, itis acceptable to begin the following frame of the charge accumulation assoon as possible. By this type of operation, it is possible to increasethe number of shooting frames per unit time by minimizing the waste ofaccumulation time.

Meanwhile, when the blur amount W is smaller (YES side of FIG. 9 S37)the microprocessor 65 reads the image data from the image pick-upelement 63 after a predetermined accumulation time elapses (FIG. 9 S38).

The microprocessor 65 takes in the image data through the imageprocessor 64 and is overwritten and recorded in the image memory 66(step S39).

Along with this type of overwriting recording, after the microprocessor65 sets the current blur amount W at the minimum blur amount W_(min)(step S40), the operation returns to step S34.

After the above-mentioned series of operations S34-40 are repeatedlyperformed until the limit time 0.5 seconds has elapsed since the releaseoperation, the microprocessor 65 moves the operation to step S41.

By the operation up to the present, the image data with the smallestblur amount W among the image data which is imaged in 0.5 seconds fromthe release operation is recorded in the image memory 66.

In this type of case (YES side of FIG. 9 S41), after the microprocessor65 image-compresses the residual image data within the image memory 66,the data is saved on the memory card 68 through the image recorder 67(FIG. 9 S43). In addition, with respect to the image compressionprocessing, instead of performing the processing here, it is acceptableto have the processing performed in step S39 shown in FIG. 9.

After saving of the image data is completed, the microprocessor 65returns the operation to step S31 after the image data within the imagememory 66 is erased in preparation for the following shooting operation(FIG. 9 S44).

Furthermore, when the blur amount W does not fall under the largestallowable value of the blur amount even one time, the image data cannotbe recorded in the image memory 66 at all. Thus, when no image dataexists in the image memory 66 (NO side of FIG. 9 S41), themicroprocessor 65 determines that blurring due to hand shaking was toomuch, so the operation returns to step S31 after processing of the“warning of blurring due to hand shaking” is performed (FIG. 9 S42).

By the operation which was explained above, in the third embodiment,image data with much less blur amount is saved in the image memory 66.Therefore, it is possible to obtain image data with less blurring due tohand shaking without using the conventional correction mechanism forblurring due to hand shaking.

Furthermore, the image data is successively overwritten and recorded inthe image memory 66, so the capacity to store at least one frame ofimage data is sufficient.

Additionally, in the third embodiment, image data with less blur amountis saved in the image memory 66 based upon the comparison of the bluramount, but the invention is not limited to this. It is also acceptableto select the image data which will be left in the image memory 66 basedupon an evaluation value including the evaluation items or the like asset forth in claims 7-10.

Furthermore, in the third embodiment, when the blur amount W does notfall below the “largest allowable value of the blur amount”, the imagedata is not recorded at all, but the invention is not limited to this.For example, the first image data or the like can be temporarilyrecorded, and after that, the image data can be updated every time theblur amount W falls below the largest allowable value. In this type ofstructure, the image data with the smallest blur amount W is eventuallyrecorded.

Additionally, in the first through third embodiments, based upon theblur amount or the evaluation value, only one frame of image data issaved, but the invention is not limited to this. For example, it is alsoacceptable to save a predetermined number of image data beginning fromthe highest ranking evaluated position based upon the blur amount or theevaluation value. In this type of structure, the operator can laterselect the image data with the best “shutter chance” among a specifiednumber of image data.

The following explains another embodiment.

Fourth Embodiment

FIG. 10 is a block diagram showing the fourth embodiment.

In FIG. 10, a zoom lens 102 is fixed at the front of an electroniccamera 101. The light-receiving face of an image pick-up element 103 isdisposed on the image space side of the zoom lens 102.

The image output from the image pick-up element 103 is connected to animage compressor 106 a via the image processor 104 which performs colorsignal processing, A/D conversion, γ correction and the like and theimage memory 105. The output of the image compressor 106 a is connectedto a microprocessor 106.

Furthermore, a memory card 108 is detachably connected to themicroprocessor 106 via an image recorder 107.

Furthermore, a release button 110 and a shooting mode selection button111 are disposed on the housing of the electronic camera 101, and theswitch outputs of these operation parts are connected to themicroprocessor 106.

Additionally, an electronic shutter control signal from themicroprocessor 106 is given to the CCD driving circuit 112. The CCDdriving circuit 112 forms a driving pulse in response to the controlsignal and gives the driving pulse to the image pick-up element 103.

Furthermore, a photometry part 113 to measure the object brightness, arange finding part 114 to measure the object distance, an encoder 115 todetect the focal distance from the lens position, and a flash part(so-called strobe) 116 are disposed on the electronic camera 101 and arerespectively connected to the microprocessor 106.

Furthermore, with respect to the corresponding relationships between theinvention as set forth in claims 1, 2 and 8 and the fourth embodiment,the image pick-up means 1 corresponds to the image pick-up element 103,the CCD driving circuit 112, and the zoom lens 102, the temporary memorymeans 2 corresponds to the image memory 105, the shooting evaluationmeans 3 corresponds to a “function to convert the image data to aspatial frequency component” of the image compressor 106 a, the stillimage selection means 4 corresponds to a “function to select image databased upon the spatial frequency component” of the microprocessor 106,and the image saving means 5 corresponds to the image recorder 107 andthe memory card 108.

The following explains the operation of the fourth embodiment.

FIG. 11 is a flow chart explaining the operation of the fourthembodiment.

First of all, when the main power is turned on to the electronic camera101, the microprocessor 106 waits until the release button 110 ispressed (NO side of FIG. 11 S1).

Here, when the release button 110 is pressed (YES side of FIG. 11 S1),the microprocessor 106 determines a current shooting mode (FIG. 11 S2).

If the current shooting mode is not any of the following cases (1)-(3),the microprocessor 106 returns the operation to step Si after anordinary shooting (shooting that images and records one frame) isperformed (FIG. 11 S3).

(1) Night view shooting mode—a mode which can cut the flash emittedlight, adjust the focus at infinite, and expose for a long period oftime.

(2) Macro mode—a mode which sets the focus of the lens at the macro areaand performs close-up shooting.

(3) Sports mode—a mode which sets the exposure time as short as possibleand shoots an object which moves at high speed.

Meanwhile, when the current shooting mode is any of these shootingmodes, there is a particularly high possibility of blurring due to handshaking, movement of the object, and/or misfocus, so the microprocessor106 performs the countermeasure operations of step S4 and after.

First of all, the microprocessor 106 instructs a plurality of sequentialshootings (3 frames as an example here) to the CCD driving circuit 112.The CCD driving circuit 112 consecutively reads three frames of imagedata from the image pick-up element 103. The three frames of the imagedata are temporarily stored in the image memory 105 after color signalprocessing, γ correction, and the like is performed by the imageprocessor 104 (FIG. 11 S4).

Next, the microprocessor 106 instructs DCT conversion (discrete cosinetransformation) to the image compressor 106 a. The image compressor 106a takes in a specified area of the screen (for example, the center ofthe screen) and performs DCT conversion with respect to three frames ofimage data within the image memory 105 (FIG. 11 S5).

The microprocessor 106 takes in the spatial frequency component afterthe DCT conversion and selects the image data including the highestspatial frequency component among the three frames (FIG. 11 S6).

Here, when there is only one piece of selected image data (NO side ofFIG. 11 S7), the microprocessor 106 moves the operation to step S11.

Meanwhile, when a plurality of selected image data are available (YESside of FIG. 11 S7), the microprocessor 106 selects the spatialfrequency component with the largest amplitude in the high area amongthe selected data (FIG. 11 S8).

Here, when there is one piece of selected image data (NO side of FIG. 11S9), the microprocessor 106 moves the operation to step S11.

Meanwhile, when there are still a plurality of selected image data (YESside of FIG. 11, S9), the microprocessor 106 selects the first shot dataamong the selected image data (FIG. 11 S10).

After the image data is thus narrowed down to one, the microprocessor106 image-compresses the image data via the image compressor 106 a, andthe image data is recorded to the memory card 108 (FIG. 11 S11).

By the operation which was explained above, in the fourth embodiment,the image data with the most ample spatial frequency component in thehigh area is selected among the image data which has been continuouslyimaged and is recorded. Therefore, it is possible to select image datain which blurring due to hand shaking, movement of the object, misfocus,or the like is appropriately small.

Furthermore, in the fourth embodiment, by using conversion such as DCTconversion, the spatial frequency component of the image data isaccurately determined, but the present invention is not limited to this.For example, it is acceptable to easily determine the spatial frequencycomponent by using a well-known spatial frequency filter (e.g., a highpass filter which takes the difference between the adjacent pixels),contrast detection, or the like.

The following explains another embodiment.

Fifth Embodiment

The fifth embodiment is an embodiment which corresponds to the presentinvention as set forth in claims 1, 2, 8, and 9. Additionally, thestructure of the fifth embodiment is virtually the same as the fourthembodiment (FIG. 10), so the structural explanation is omitted here.

FIG. 12 is a flow chart explaining the operation of the fifthembodiment.

The following explains the operation of the fifth embodiment inaccordance with FIG. 12.

First, when the main power is turned on to the electronic camera 101,the microprocessor 106 waits until the release button 110 is pressed (NOside of FIG. 12, S1).

Here, when the release button 110 is pressed (YES side of FIG. 12 S1),the microprocessor 106 measures the object brightness through thephotometry part 113 and determines the exposure time to obtain theappropriate exposure (FIG. 12 S2).

Next, the microprocessor 106 detects the focal distance of the zoom lens102 through the encoder 115. Furthermore, the microprocessor 106 detectsthe object distance through the range finding part 114 (FIG. 12 S3).

Here, the microprocessor 106 determines whether the current mode settingis the flash shooting mode (FIG. 12 S4). In the case of the flashshooting mode, the possibility of blurring due to hand shaking ormovement of the object is lower, so the microprocessor 106 returns theoperation to step S1 after ordinary shooting (shooting to image andrecord one frame) is performed (FIG. 12 S5).

Meanwhile, when the current mode setting is other than the flashshooting mode, the microprocessor 106 performs the following conditiondeterminations (1) and (2).

(1) Whether the exposure time is longer than a specified time τ.

(2) Whether the image magnification (approximately equal to focaldistance/object distance) is larger than a specified magnification γ.

When neither of these conditions are established (NO side of FIG. 12S6), the microprocessor 106 determines that there is little possibilityof blurring due to hand shaking or movement of the object, and theoperation is returned to step S1 after the ordinary shooting isperformed (FIG. 12 S5).

Meanwhile, when either of these conditions is established (YES side of

FIG. 12 S6), the microprocessor 106 performs the countermeasureoperation of step S7 and after.

First, the microprocessor 106 instructs continuous shooting of aplurality of frames (3 frames as an example here) to the CCD drivingcircuit 112. The CCD driving circuit 112 sequentially reads three framesof image data from the image pick-up element 103. The three frames ofimage data are temporarily stored in the image memory 105 through theimage processor 104 after color signal processing, γ correction, and thelike is performed (FIG. 12 S7).

Next, the microprocessor 106 instructs image compression to the imagecompressor 106 a. The image compressor 106 a compresses one frame ofimage data for testing and determines an appropriate scale factor (awell-known parameter value to govern the condition of quantization inthe image compression) in order to approach a desired compressionencoding amount. The image compressor 106 a uniformly uses the scalefactor value and sequentially image-compresses three frames of imagedata (FIG. 12 S8).

Here, the microprocessor 106 compares the sizes of the encoding amountsafter compression (compressed encoding amounts) of the three frames ofimage data and selects the image data with the largest compressedencoding amount (FIG. 12 S9).

Here, when there is one piece of selected image data (NO side of FIG. 12S10), the microprocessor 106 moves the operation to step S12.

Meanwhile, when there are a plurality of selected image data (YES sideof FIG. 12 S10), the microprocessor 106 selects the data which was firstshot among the selected image data (FIG. 12 S11). (FIG. 12 S12).

By the operation which was explained above, in the fifth embodiment, theimage data with the largest compressed encoding amount is selected amongthe image data which has been continuously imaged and is recorded to thememory card 108. Therefore, the image with generally little blurring dueto hand shaking, movement of the object, and misfocus and with the mostample spatial frequency component in the high area can be recorded ontothe memory card 108.

Furthermore, in the fifth embodiment which was described above, when theimage magnification is larger than the specified magnification γ, it isin a mode that selects a good image (an image in a good shooting state),but the invention is not limited to this. For example, it is acceptableto enter a mode which selects a good image when the focal distance islonger than the specified value.

Furthermore, in the fifth embodiment which was described above, threeframes of image data are image-compressed over the entire screen, butthe present invention is not limited to this. For example, it is alsoacceptable to extract only a specified area (for example, the center ofthe screen) on the screen from the three frames of image data, performthe image compression, and obtain the compressed encoding amount forevaluation. In this type of operation, the comparison of the spatialfrequency component is performed limited to the specified area.Therefore, even if it is in a shooting condition where the backgroundmight be blurry such as zoom shooting or wide-angle shooting, it ispossible to accurately select clear image data within the specifiedarea. Furthermore, when the compressed encoding amount for evaluation isobtained, image compression for only the specified area is sufficient,so it is possible to significantly shorten the processing time to obtainthe compressed encoding amount for evaluation.

In addition, in the fifth embodiment which was described above, afterthree frames of continuous shooting are all completed, three frames ofimage compression begins, but the present invention is not limited tothis. For example, it is acceptable to increase the number of shootingper unit time by simultaneously performing the previous frame of imagecompression and the following frame of image pick-up operation.Particularly, in this type of operation, it is possible tosimultaneously perform the image pick-up operation along with the oldand new comparison of the compressed encoding amount, so it is possibleto structure an electronic camera to overwrite and record better imagedata such as the present invention.

Furthermore, in the first through fifth embodiments which were describedabove, the case is explained in which one good image is saved, but it ispossible to apply the present invention to a case in which a pluralityof good images are saved. For example, in the case of exposurebracketing (a mode that shoots several times while changing the exposurecondition), the operation to save one good image under the same exposurecondition can be repeated while changing the exposure condition.

Furthermore, in the first through fifth embodiments which were describedabove, the display function of the electronic camera is not particularlyexplained, but it is possible to perform various displays related to thepresent invention. For example, a mode display such as “a mode to selectan image in response to a good/bad evaluation of the shooting state” maybe performed within the view finder, and/or on the monitor screen of theelectronic camera, and/or the number of the current sample of image dataand/or the number of remaining samples can be displayed by usingpictures, characters, or the like. With this type of structure, it ispossible to inform the photographer of the operation state of theelectronic camera in detail.

In addition, the result of a good/bad evaluation of the shooting state(size of the blur amount or the like) can be displayed by usingpictures, characters, or the like. At this time, along with the displayof a good/bad evaluation, it is acceptable to display (for example,thumbnail display) the image data which is temporarily stored. With thistype of structure, the photographer considers the image display and thedisplay of a good/bad evaluation and can appropriately select desiredimage data.

Furthermore, when the good/bad evaluation in a shooting state is lessthan a threshold, a warning display (including a warning or the like)can be performed, and/or a display to inform that the good/badevaluation is the maximum (including a warning or the like) can beperformed. In this type of structure, the photographer is informed ofthe goodness or badness of the shooting state, so it is possible to leadthe shooting to a better shooting state.

Furthermore, in the above-mentioned embodiment, the electronic camera ofa unitary structure is explained, but the present invention is notlimited to this. For example, it is possible to apply the presentinvention to an electronic camera which is separately structured by animage pick-up unit and information equipment (computer or the like).

As a specific example of the above case, the operations can be dividedinto: (1) The image data which is continuously imaged in the imagepick-up unit side is temporarily stored. (2) An image is selected andsaved among a series of image data in response to the good/badevaluation of the shooting state by the program execution of thecomputer side.

Furthermore, when the present invention is applied to a computer, it isacceptable to independently perform “the image selection program toselect and save an image among a series of image data in response to thegood/bad evaluation of the shooting state” on the computer side.Needless to say, in this type of structure, there is a disadvantage suchthat the collection of information of the shooting state from the cameraside is insufficient, but it is possible to perform the operation as asingle computer if the good/bad evaluation of the spatial frequencycomponent is available, so it is possible to obtain almost the sameoperation effect as the structure in the present invention.

In the invention, the image data which has been imaged during the periodof time when the shooting state is the best is selected from among theimage data which has been continuously imaged. Therefore, it is possibleto obtain image data in a good shooting state without using theconventional correction mechanism for blurring due to hand shaking.

Therefore, it is possible to omit the optical system for theconventional correction of blurring due to hand shaking, and sizereduction and weight reduction of the shooting lens can be improved.

Furthermore, it is possible to omit the space to dispose the opticalsystem for the correction of blurring due to hand shaking from theshooting lens. As a result, the degree of freedom becomes high in termsof the optical design, and the aberration performance and the like ofthe shooting lens can be optimized without any difficulty.

Furthermore, the slight internal reflection which occurs in the opticalsystem for the conventional correction of blurring due to hand shakingcan be solved. Therefore, the flare during backlight shooting can bedecreased and the camera image quality can be significantly improved.

Furthermore, it is possible to omit the driving mechanism for theconventional correction for blurring due to hand shaking or the like,and electricity conservation in the electronic camera can be improved.Additionally, problems such as noise and vibration from the drivingmechanism for the correction for blurring due to hand shaking can besolved.

Furthermore, the selection processing of the image data is performedafter the shooting is completed, so there are advantages such that theprocessing load during the shooting period does not significantlyincrease and the number of shooting frames per time unit does notdecrease much.

In the invention, the temporary memory means begins the temporarystorage of the image data after the release operation of the electroniccamera. Because of this, it is possible to stop the image pick-upoperation prior to the release operation. Accordingly, electricityconservation for the electronic camera can be improved.

In the invention, the temporary memory means maintains the image datafrom before to after the release operation. Accordingly, not limited tothe image data after the release operation, it is possible to accuratelyselect the image data in a much better shooting state from the periodspanning from before to after the release operation.

Furthermore, blurring due to hand shaking has not yet occurredimmediately before the release operation in accordance with the releaseoperation. Therefore, when blurring due to hand shaking is evaluated asa shooting state, by adding the period immediately before the releaseoperation to the sampling range of the image data, it is possible toselect the image data with extremely little blurring due to hand shakingat high probability.

Furthermore, the sampling range of the image data spans from before toafter the release operation, so the worst value of the release time lag(equivalent to the edge point of the sampling range of the image data)can be decreased by almost half compared to the case when the samplingrange of the same time length begins with the release operation.

In the invention, the temporary memory means and the image saving meansuse the same memory mechanism. Therefore, there is no need for a memorymechanism for only the temporary memory means, and it is possible tosimplify the construction of the electronic camera.

In the invention, the image data which is continuously imaged isdifferentially compressed and then is temporarily stored. Therefore, itis possible to keep the encoding amount of the image data small and tominimize the memory capacity of the temporary memory means.

Furthermore, if the memory capacity of the temporary memory means doesnot change, it is possible to increase the number of samplings of theimage data which can be temporarily stored. In this case, because theselection is performed among more image data, the possibility ofobtaining image data in a much better shooting state can besignificantly higher.

In the invention, image data in a much better shooting state isselectively retained among the image data which is continuously imaged.Therefore, it is possible to obtain image data in a good shooting statewithout using the conventional correction mechanism for hand shaking orthe like.

Additionally, image data is overwritten and recorded in the memorymedium, so it is sufficient to have merely enough capacity to store atleast one frame of image data. Therefore, it is not necessary to have alarge capacity memory medium for temporary storage, and it is possibleto simplify the construction of the electronic camera.

In the invention, as a good/bad evaluation of the shooting state, theblur amount of the image pick-up means is detected. As a result, it ispossible to select and save the image data with appropriately littlehand shaking.

In the invention, as a standard of a good/bad evaluation of the shootingstate, the spatial frequency component of the image data is used. As aresult, it is possible to select and save image data with appropriatelylittle overall blurring due to hand shaking, movement of the object, andmisfocus.

Particularly, this type of good/bad evaluation of the spatial frequencycomponent can be performed by a calculation, so a piezoelectric gyro orthe like for the detection of blurring due to hand shaking is notneeded. Therefore, even if the invention as set forth in claim 8 isused, it is not particularly necessary to add a sensor part or the liketo the conventional electronic camera, and it is possible to obtain theeffects of the present invention with a simple structure at low cost.

Furthermore, particularly, with respect to an object showingunpredictable movement such as a flower swayed by the wind, it isextremely difficult to completely prevent misfocus by ordinary AF(autofocus) shooting only. However, in the invention as set forth inclaim 8, even under a bad condition like this, based upon the spatialfrequency component, it is possible to reliably select and save theimage data with little misfocus.

In the invention, the high-area component amount of the spatialfrequency is determined by the compressed encoding amount. This type ofvalue of the compressed encoding amount can be obtained by the result ofconventional image compression processing or the like, so it is notnecessary to add a particular calculation processing, and it is possibleto decrease the processing time and the calculation processing amount.

In the invention, for the good/bad evaluation of the shooting state, therelease time lag is used. As a result, it is possible to select and savegood image data with comparatively little release time lag.

Especially, in a state where temporary storage of the camera image hasbeen performed since before the execution of the release operation, whenimage data with little release time lag is selected, it is possible toobtain image data where the release time lag is extremely close to 0.

1. An electronic camera comprising: image pick-up means for continuouslyimaging an object; a memory medium that stores image data; shootingevaluation means that obtains one evaluation relating to a blur amountof the electronic camera for each image data continuously shot by theimage pick-up means according to an operation of a release button forrecording image data and evaluates a good or bad shooting state for eachframe by the evaluation; comparison means for comparing the evaluationof said shooting evaluation means concerning the image data within saidmemory medium with the evaluation of said shooting evaluation meansconcerning new image data from said image pick-up means; imageoverwriting means for overwriting and recording an entire frame of thenew image data to said memory medium when the evaluation of the newimage data is higher than the evaluation of the image data within thememory medium in accordance with a comparison result of said comparisonmeans; and image recording means for recording, on a memory card,residual image data that remains on the memory medium at a point in timeat which the continuously imaging has ended.
 2. The electronic camera asset forth in claim 1, wherein, as at least one of the good or badevaluations of said shooting state, said shooting evaluation meansdetects a blurring amount and/or a misfocus amount of said image pick-upmeans.
 3. The electronic camera as set forth in claim 2, wherein, as atleast one of the good or bad evaluations of said shooting state, saidshooting evaluation means determines a spatial frequency component ofsaid image data.
 4. The electronic camera as set forth in claim 3,wherein said shooting evaluation means determines a high-area componentamount of the spatial frequency, based upon a compressed encoding amountof said image data.
 5. The electronic camera as set forth in claim 4,wherein, as at least one of the good or bad evaluations of said shootingstate, said shooting evaluation means determines a release time lag,which is a time difference between a release operation of the electroniccamera and an image pick-up time of the image data.
 6. An electroniccamera comprising a controller that: obtains one evaluation relating toa blur amount of the electronic camera based on a spatial frequencycomponent for each image data continuously shot according to anoperation of a release button for recording image data and evaluates agood or bad shooting state for each frame by the evaluation; comparesthe evaluation concerning image data within a memory medium with theevaluation concerning new image data; overwrites and records an entireframe of the new image data to said memory medium when the evaluation ofthe new image data is higher than the evaluation of the image datawithin the memory medium in accordance with a comparison result of theevaluation concerning the image data within the memory medium with theevaluation concerning the new image data; and recording, on a memorycard, residual image data that remains on the memory medium at a pointin time at which continuously imaging has ended.